This invention relates to an apparatus and method for aligning couplings of rotating shafts, particularly large, high speed shafts such as used in electric power plants and other large industrial operations. Manufacturers of high speed rotating equipment provide specifications for desired alignment and limits of deviation. Operation outside of these recommended norms can cause damage to equipment, vibration and other problems. Manufacturers also require a process that rotates both shafts to record the alignment relationship between the two rotors. Each rotor can be rotated separately or the rotors can be temporarily connected with soft metal pins. The rotation of each coupling separately requires additional time to rotate each rotor. Connecting pins cause deflection of the couplings due to binding with time required to free the pins. Neither process will stop the coupling rims with the correct degree position to allow use of new laser alignment tooling that is now available. The cam pin according to the present invention, when used without the cam sleeve according to the present invention, provides a process to record coupling alignment readings that are free of errors due to deflection of the couplings and stops the rims with the degree of relationship required for the use of laser tooling. The cam pin and sleeve used together provides a process that is safer and faster than the other processes. Prior art methods include use of a crane to rotate the shafts, and while this process can be acceptable from an accuracy standpoint, the process can frequently cause accidents. The time required to complete alignment and assemble couplings effects the time the equipment is out of service, and should therefore be reduced to a minimum. Another prior art device, referred to as a xe2x80x9cHutterxe2x80x9d turning pin, uses a pin which is split so that it separates into two halves for insertion and removal from the rotor couplings for aligning the rotors. A Hutter coupling runout eliminator pin corrects differential runout prior to line boring and aligns coupling bolt holes in a manner similar to the turning pins.
Use of the cam pin and sleeve according to the invention shortens the time that equipment must be out of service for alignment.
With tandem rotors, all of the rotors can be connected with a cam pin in each coupling and the shafts all rotated together. The cam pins are unlocked at each data point to assure that the data is not corrupted by binding, and then locked again for the next rotation. The rotors can be rotated with drive equipment supplied by the manufacturer or any other suitable device that can impart slow, even rotation to the rotors.
Therefore, it is an object of the invention to provide a cam pin for aligning couplings of rotatable shafts.
It is another object of the invention to provide a cam pin which can be used for taking alignment data points off of couplings of rotatable shafts.
It is another object of the invention to provide a cam pin which can be used in combination with a rotatable cam sleeve to achieve highly accurate alignment of couplings of rotatable shafts.
It is another object of the invention to provide a method of using a cam pin with or without a cam sleeve to achieve the foregoing objects.
These and other objects of the present invention are achieved in the preferred embodiments disclosed below by providing an apparatus for precisely aligning bolt holes in first and second adjacent drive shaft couplings, comprising a cam pin for being positioned in the generally aligned bolt holes in the shaft couplings and rotated to bring the bolt holes in to more precise alignment. The cam pin includes a first, relatively large diameter segment having a cylindrical wall defining a first longitudinal axis for being positioned in a precisely fitting condition in the bolt hole of the first coupling, and a second, relatively small diameter segment having a cylindrical wall defining a second longitudinal axis offset from and eccentric to the longitudinal axis of the first segment for being relatively loosely positioned in the generally aligned bolt hole of the second coupling. A cam sleeve is provided for being positioned in axial and rotational sliding relation over the small diameter segment of the cam pin and within the bolt hole of the second coupling. The cam sleeve has an offset bore defining a progressively varying wall thickness whereby rotation of the cam pin and cam sleeve relative to each other and to the bolt holes within which they are positioned brings progressively varies the overall diameter of the cam pin to bring the bolt holes into precise alignment for installation of the connecting bolts.
Preferably, the cam pin includes rotation means for aiding in rotation of the cam pin in the bolt holes.
According to one preferred embodiment of the invention, the rotation means comprises a hexagonal end cap positioned on one end for receiving a suitably-sized hex wrench. According to another preferred embodiment of the invention, the hexagonal end cap is positioned on the large diameter segment of the cam pin.
According to yet another preferred embodiment of the invention, the cam pin includes a stop collar for being positioned on the large diameter segment of the cam pin for preventing damage to the coupling.
According to yet another preferred embodiment of the invention, a cam pin is provided for precisely aligning bolt holes in first and second adjacent drive shaft couplings, and comprises a cam pin for being positioned in generally aligned bolt holes in the shaft couplings and rotated to bring the bolt holes in to more precise alignment. The cam pin includes a first, relatively large diameter segment having a cylindrical wall defining a first longitudinal axis for being positioned in a precisely fitting condition in the bolt hole of the first coupling, and a second, relatively small diameter segment having a cylindrical wall defining a second longitudinal axis offset from and eccentric to the longitudinal axis of the first segment for being relatively loosely positioned in the generally aligned bolt hole of the second coupling. Rotation of the cam pin within the bolt holes within which it is positioned progressively varies the overall diameter of the cam pin to bring the bolt holes into alignment for installation of the connecting bolts.
A method for precisely aligning bolt holes in first and second adjacent drive shaft couplings in accordance with a preferred embodiment of the invention comprises the steps of positioning a cam pin into generally aligned bolt holes in the shaft couplings. The cam pin includes a first, relatively large diameter segment having a cylindrical wall defining a first longitudinal axis for being positioned in a precisely fitting condition in the bolt hole of the first coupling, and a second, relatively small diameter segment having a cylindrical wall defining a second longitudinal axis offset from and eccentric to the longitudinal axis of the first segment for being relatively loosely positioned in the generally aligned bolt hole of the second coupling. The cam pin is rotated within the bolt holes to bring the bolt holes in to more precise alignment.
According to yet another preferred embodiment of the invention, the method includes the further step of positioning a cam sleeve in axial and rotational sliding relation over the small diameter segment of the cam pin and within the bolt hole of the second coupling, said cam sleeve having an offset bore defining a progressively varying wall thickness, and rotating the cam pin and cam sleeve relative to each other and to the bolt holes within which they are positioned to progressively vary the overall diameter of the cam pin and thereby bring the bolt holes into precise alignment for installation of the connecting bolts.
Some of the objects of the invention have been set forth above. Other objects and advantages of the invention will appear as the invention proceeds when taken in conjunction with the following drawings, in which:
FIG. 1 is a perspective view of a pair of shafts in coupled relation with a cam pin according to an embodiment of the invention in one pair of aligned bolt holes;
FIG. 2 is a first perspective view of a cam pin according to an embodiment of the invention;
FIG. 3 is a second perspective view of the cam pin according to an embodiment of the invention shown in FIG. 2;
FIG. 4 is a cross-sectional view along the longitudinal axis of the cam pin;
FIG. 5 is a vertical cross-sectional view of the joined couplings shown in FIG. 1;
FIG. 6 is a perspective view of a cam sleeve according to an embodiment of the invention; and
FIG. 7 is a vertical cross-sectional view of a pair of joined couplings with both a cam pin and cam sleeve positioned in one aligned pair of bolt holes according to FIG. 1.